A direct route from white phosphorus and fluorous alkyl and aryl iodides to the corresponding trialkyl- and triarylphosphines
Reactions of white phosphorus (P4), fluorous alkyl iodides I(CH2)mRfn (Rfn = CF3(CF2)n−1; 4.0–5.0 equiv./P), and SmI2 (1.0–1.5 equiv./iodide) in THF afford the corresponding trialkylphosphines P((CH2)mRfn)3 (m,n = 2,8; 2,10; 3,6; 3,8; 4,8; 58–92% after workup). Similar reactions with the fluorous aryl iodides IC6H4(3-Rf6), IC6H4(4-Rf6), and IC6H3(3,5-Rf6)2 require the stronger reductants SmBr2 or SmCl2 and give the triarylphosphines P(C6H4(3-Rf6))3, P(C6H4(4-Rf6))3, and P(C6H3(3,5-Rf6)2)3 (23–41%). These transformations involve non-chain radical additions to P4. Advantages versus existing routes to fluorous phosphines, and general strategic issues in the synthesis of organophosphorus compounds, are discussed.